A vertical retraction syndrome was present in both eyes of two children of a sibship of five. Ocular motility was normal in the remainder of this family; however, incomplete situs inversus of the optic nerve-head was present in one of the children with the vertical retraction syndrome and in an otherwise normal brother. The clinical features of the vertical retraction syndrome are similar to Duane's syndrome although they affect different muscles. The results of the forced duction test indicate that structural rather than neurogenic anomalies are probably the cause of the vertical retraction syndrome in these cases.
Khodadoust AA, von Noorden GK. Bilateral Vertical Retraction SyndromeA Family Study. Arch Ophthalmol. 1967;78(5):606-612. doi:10.1001/archopht.1967.00980030608009